Hyrachyus obliquidens was named by Scott and Osborn (1887) [Colbert and Schoch 1998 list this as a synonym of Helaletes nanus but give no specific justification for their action and fail to mention the combination Dilophodon nanus, so I believe that they have accidentally confused the two species ].

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.